[uCsimm] pulse detect

From: James Wilson (jc.wilson@utoronto.ca)
Date: Thu Nov 02 2000 - 19:39:46 EST

        I want to detect a 0.5micro second pulse (STROBE) on
     the ucsimm?s PD0 port and, when this occurs, set a pin
     low (BUSY), then read 8 data pins on another port .
     At first I thought I could loop and wait for the pulse
     but the latency for the small bit of code I wrote was
     around 80microsecons way tooooo long for my
     application. Could anyone suggest a better way to
     do this? I have the following ideas but I'm not
     sure which one would be the easiest to implement.

     1. Use a machine language subroutine to monitor the
     2. Use interrupt INT0 .
     3. Use interrupt INT0 as in (2) but mask the interrupt
     and loop checking the interrupt pending register for
     any change.
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